The uses of tea in the healthy system / by Edward Smith.

  • Edward Smith
Date:
1861
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Licence: Public Domain Mark

Credit: The uses of tea in the healthy system / by Edward Smith. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    but it is not said “to nourish or fatten,” and it is af- firmed to “remove impurities,” which must mean the removal of wasted and useless material, and not the supply of new material for digestion and transformation. Beers have been found to fatten the body, but it would be a new thing to feed a person on tea We should expect such a person to become “small by degrees and beautifully less.” Hence it is important to consider how far this statement, as to the nutritive properties of tea, is borne out either by the chemical composition of the leaf or by actual scientific observation of its effects upon the human system. The statement that tea cheers and removes impurities mani- festly implies that it increases the transformation of food or tissue, for to cheer implies increased nervous action, and to remove material implies waste of the body ; and hence, on the one hand, popular experience informs us that tea causes waste, and, on the other, science is appealed to to show that tea nourishes the hod)'. Either these opinions contradict each other ; or, as it may be possible to show, they are both, in a degree, true. There are thus three questions raised in reference to the influence of tea :— 1. The waste of the body is lessened. 2. The body is nourished. 3. By lessening waste we may lessen supply, and yet the bodily powers shall be duly sustained. We will first offer a few remarks upon each of these questions. Now as to the value of theine, or the active principle of tea, in retarding waste of the body. It is to be observed that it has been deduced from the statement that it lessens the amount of nitrogenous or flesh-forming material which is thrown out of the body, and this has been stated on the authority of many, and is held to mean that thus the waste of the flesh of the body is lessened. This last assertion was the opinion which Liebig intro- duced, and which has, until recently, controlled tire scientific world. But now it is known that the waste of nitrogen, or the so-called flesh-forming material which is said to be lessened by tea, depends clearly upon at least thiee things:—1. The destruction of those tissues of the body which are composed of nitrogen ; 2. The mere kind of food taken, as gelatine, for example, which, whilst it has small power to nourish the body, increases largely the excretion of nitrogen ; and 3, Quantity, or perhaps excess of food, for two distinguished members of this Society, Messrs. Lawes and Gilbert, have shown incontestibly that, if two pigs are fed on foods varying in the amount of nitrogen which they contain, they will differ in the same proportion in the amount of nitrogen which they will throw out. When, therefore, the excreted nitrogen may proceed from excess of food, or kind of food, or perhaps from unassimi- lated food, as well as from the tissues of the body, it is idle to regard its diminution as necessary evidence of the lessened waste of tissue. Hence, Prof. Johnstone’s grounds for commending the use of tea cannot be conceded. The different methods of inquiry to which I referred in my former paper are doubtless the causes of the discrepancy and errors in the results obtained by various observers. When doses of tea are added to, or given in place of, sub- stances of unknown influence acting upon the system at the same time, it is impossible to determine their separate effect with certainty. As well might a banker keep the accounts of a particular customer, who had paid money into, and received money out of, the bank during the day, by placing to his debit or credit whatever difference might appear in the general cash at the end of that day, as com- pared with the amount noted at the end of the previous day, when hundreds had also paid in and received out variable sums on both days. Yet such has been the method adopted by those who affirm that tea lessens the waste of the body. Bilker, whose experiments are more extended than those of any other observer, when comparing the effects of tea and coffee with other foods, fell into the great error of omitting a pint or even a quart of milk for breakfast when he took tea or coffee, and of drinking it when he would compare the two sets of results together. Now, tea and coffee offer scarcely any nitrogen to the system, whilst milk gives 44 grains in every pint, and hence he might well find that less nitrogen was given out when tea or coffee was taken than when milk was taken, but without at all showing that the tea or coffee lessened the excretion of the nitrogen. But opposed to these results we have those of Profess sor C. G. Lehmann and my own. Professor Lehmann, a most distinguished German chemist and physiologist, and the most distinguished writer on physiology on the Continent of Europe, found the contrary, and proved that tea increases the emission of such compounds ; and he re- marks that he cannot say whether this was due to the increase of all the vital actions of the body which accom- panied its use, and which would cause increased waste of all kinds, or to the nitrogen which it contained, and which, being in excess of the wants of the body, would thus be thrown off.—(Physiol. Chemistry, Yol. II., p. 419.) In some experiments which we made upon four prisoners, kept under absolutely uniform conditions, to whom we gave tea and coffee each for three days during a part of the inquiry, we found a diminution in the excretion of nitrogen but for one day only, and at the end of the six days the quantity was more than 30 grains per day greater than it had been on the day before the experiment began, as is shown in the diagram on the wall. During this period, however, there was no diminution in the quantity of water eliminated. That there is increased and not decreased vital action due to tea is familiar to us in its effect in preventing sleep ; and is affirmed by the Chinese, when they state that “ if it be drunk too freely it will produce exhaustion and lassitude,” and if there be increased action in the body, there must be increased waste, as surely as that a wheel cannot be driven round with increasing velocity without causing increased friction, and increased waste of its own structure, or of the lubricating oil, or of the sub- stance upon which it revolves. Hence we think that on this evidence the property of theine in retarding waste, and thereby lessening the necessity for food, must submit to the Scottish verdict of “ not proven.” Then as to the gluten, which is said to nourish the body. Good tea leaves contain 20 per cent, of gluten, but boiling water will take up only 16 per cent, of the leaf, including all the four substances already referred to, and hence the amount of gluten which we actually drink in an infusion of tea cannot exceed about 8 per cent, of the weight of the tea leaves employed. Now, if we use the eighth part of an ounce of tea, or 55 grains, the total available gluten would be about four grains, and this quantity contains two-thirds of a grain of nitrogen. If we assume that the quantity of tea employed at a meal is twice that just mentioned, and that it is taken two or three times a day, we shall see the utter insignificance of its gluten when compared with the 250 grains of nitrogen which is otherwise supplied in food and also evolved from the body daily. Hence it is quite clear that we cannot regard tea as a nutritious food simply because it affords this very minute quantity of nitrogen or flesh-forming ma- terial ; but although the theory cannot be sustained on the ground indicated, we hope to be able to show that there is a sense in which tea by its gluten may improve nutrition, whilst in other conditions it may waste the system. The real ground of Professor Johnstone’s theory is not, however, the quantity of nitrogen supplied, but the inde- finite assertion that by some unknown means it lessens the waste of the system. Now, as to the advantage of lessening waste and supply. Having very recently in this room had occasion to discuss the question of waste, I will only now remind you of the fallacy of assuming that in a state of health you may lessen the waste for a long period with benefit to the system, for there must manifestly be a proper balance maintained between want and supply, and if you lessen both, as Professor Johnstone